Rotary impact wrench



p 1951 w. F. SINDELAR 3,001,429

' ROTARY IMPACT WRENCH Filed April 16, 1959 4 Sheets-Sheet 1 I N VENTOR. A//Zz/4M 6/11/0544 ,4 rrapA/sy Sept. 26, 1961 w. F. SINDELAR ROTARY IMPACT WRENCH 4 Sheefs-Sheet 2 Filed April 16, 1959 v INVENTOR. MZz/4M 1? 5/4/0424? BY 17/0 /135 Mm/u/A/y f I-WPIP/MGI-QA/ dfraP Sept. 26, 1961 w. F. SINDELAR ROTARY IMPACT WRENCH 4 Sheets-Sheet 3 Filed April 16, 1959 Sept. 26, 1961 w. F. SINDELAR 3,001,429

ROTARY IMPACT WRENCH Filed April 16, 1959 4 Sheets-Sheet 4 y INVENTOR.

United States Patent 3,001,429 ROTARY IMPACT WRENCH William F. Sindelar, Cleveland, Ohio, assignor, by mesne assignments, to Master Power Corporation, Bedford, Ohio, a corporation of Maryland Filed Apr. 16, 1959. Ser. No. 866,852 19 Claims. (Cl. 815Z.3)

This invention relates to an impact wrench and more particularly to an impact wrench having an anvil and a rotating hammer portion which is moved axially into and out of the path of the anvil to impart impacting blows to the anvil.

Numerous expedients have been employed to convert the rotary motion of a driving motor to intermittent impact blows against an anvil carried byan output shaft. Generally a massive hammer is rotated by the motor and the energy of the rotating hammer is intermittently dissipated by rotary blows against an anvil carried by the output shaft. Some of the prior art devices have included an axially slidable hammer dog which is carried by the rotary hammer and is adapted to be moved axially in and out of the path of the anvil portions. In some instances the hammer dog of the prior art was spring-biased out of the path of the anvil portions. Such arrangements under certain operating conditions resulted in the transmission of torque to the anvil shaft independently of the hammer dogs. Other prior art constructions have provided air and hydraulic piston and cylinder arrangements to move the hammer dog into or out of the path of the anvil portions. The prior art efforts to move the hammer dog into and out of the anvil path with cam devices have not succeeded since such prior art efllorts included a rotary drive to the rotary hammer independently of the rotary drive to the hammer dog.

The present invention avoids the use of springs, air and hydraulic pistons and provides a novel arrangement of cam and ball devices which are effective to move a hammer dog axially into the path of the anvil to accomplish an impact blow and thereafter retract the hammer dog axially out of the path of the anvil.

It is among the objects of my invention to provide an impact wrench having a driving shaft rotated by a motor and a driven shaft to rotate a nut, bolt, or the like, where in the driven shaft is provided with an anvil and wherein the driving shaft is provided with a rotating hammer having a hammer dog arranged to be moved in and out of the path of the anvil as may be determined by the torque requirements of the nut or bolt and the torque imposed by the driving shaft.

It is a further object of my invention to provide an impact Wrench according to the preceding object wherein the rotating hammer dogs and the driving shaft and the anvil shaft are provided with spaced cams which move the hammer dog into the path of the anvil and withdraw the hammer dog from the path of the anvil.

It is a further object of my invention to provide an impact wrench according to the preceding objects wherein the anvil is provided with a cam shaft to rotate therewith and wherein the hammer dog is moved in and out of the path of the anvil by a ball interposed between a cam on the cam shaft and a cam slot on the hammer dog.

It is a further object of my invention to provide an impact wrench according to the preceding object wherein the input driver of the wrench is provided with a triangular cam recess and wherein the hammer dog is provided with a triangular recess and a ball is arranged to cooperate with both of said cam recesses to rotate the hammer and also withdraw the hammer dog from the anvil after the hammer dog has exerted an impacting blow against the anvil.

Further objects and advantages relating to efliciency in operation, ruggedness of construction, ease of service and long life will appear from the following description and the appended drawings wherein:

FIG. 1 is an elevation showing an impact wrench made according to my invention and including a motor unit to drive the wrench;

FIG. 2 is an exploded view showing the principal components of the impacting wrench arranged in the order in which they are disposed in the wrench;

FIG. 3 is an elevation in section of the preferred form of impact wrench as assembled;

FIG. 4 is a transverse sectional view taken as indicated at 4- 4 of FIG. 3;

FIG. 5 is a developed showing of the anvil cam and the recess in the hammer dog and the ball cooperating therewith to move the hammer dog toward the anvil;

FIG. 6 is a plan view showing the impacting mechanism with the hammer dog in its retracted position;

FIG. 7 is a plan view similar to FIG. '6 but showing the hammer dog in its advanced position;

FIG. 8 is a sectional View taken on the plane indicated at 8-8 of FIG; 3;

FIG. 9 is a sectional view taken at the broken planes indicated at 9-9 of FIG. 3;

FIG. 10 is an elevation with parts in section of a modified form of impact wrench;

FIG. 11 is a plan view of the impact wrench of FIG. 10 showing the hammer dog in retracted position;

FIG. 12 is a view similar to FIG. 11 showing the hammer dog in its advanced position;

FIG. 13 is a perspective View of the hammer dog element employed in the modification of FIG. 10;

FIG. 14 is a developed showing of the anvil cam and the ball cooperating therewith to advance the hammer dog;

FIG. 15 is an elevation showing the anvil cam element employed in the modification of FIG. 10;

FIG. 16 is a developed showing of the cam recess employed for retracting the hammer dog in the modification of FIG. 10; and

FIG. 17 is an elevation of the driving element of the impact wrench which is provided with the cam recess shown in FIG. 16.

Referring to the drawings, the impact wrench made according to my invention is illustrated in its entirety in FIG. 1 wherein 6 indicates a motor element for driving the impact mechanism 7 within the housing 11 and the output shaft 8 which is adapted to receive socket wrenches or the like for drawing up nuts or bolts. The motor unit 6 is preferably an air motor which is reversible so as to rotate the output shaft 8 in either direction. It Will be understood by those skilled in the art that other reve r sible motors such as hydraulic motors may be used to drive the impact mechanism.

Integrally formed with the outputt shaft 8 is an anvil indicated in its entirety as at 9. The cylindrical shaft portion 10 of the anvil is adapted to rotate within a bearing 10a carried by the housing 11 of the impact mechanism 7. The anvil 9 includes anvil portions 12 and 13 which are oppositely disposed with respect to the axis of the anvil shaft so as to cooperate with hammer dogs 14 and 15, respectively. It will be understood as the description proceeds that the anvil portion 12 is provided with a face 12a and the anvil portion 13 is provided with a face-13a and that when the hammer is driven in a clockwise direction the hammer dog face 14a strikes the face 12a and at the same time the face 15aon the hammer dog 15 strikes the face 13a on the anvil portion 13. Similarly when the impact wrench is driven in a counter-clockwise direction the hammer dogs are adapted to be brought into the path of the anvil so that face 14b of the hammer dog 14 strikes the face 12b on the anvil portion. 12. Similarly the opposite face 15b (not shown) of the hammer dog 15 will strike the face 13b of the anvil. The angular open space between the anvil portions 12 and 13 is referred to herein as the anvil path.

The anvil is provided with a central bore 17 adapted to receive the forward end of the cam shaft 18. To nonrotatably mount the shaft 18 in the anvil, opposed slots 19 are formed in the end face of the anvil in the bore 17 so as to receive half of the spheres 20 and 21 carried in hemispherical recesses 22 in the shaft 18. This construcfion permits the forward end of shaft 18 to be secured to the anvil after the shaft has been passed through an opening in the hammer dog 40 during assembly.

The intermediate portion of the cam shaft 18 is provided with a cam 23 having oppositely sloping cam faces 24 and 25. The rearward end of the shaft 18, as at 18a, is journalled within a bore 27 extending axially into the driving member 30. That end of the driving member 30 adjacent the driving motor 6 is internally splined as at 31 to receive cooperating portions formed on the end of the motor shaft 32. The driving member 30 is provided with a triangular cam recess 36 adapted to receive the ball 34 which cooperates with an oppositely disposed triangular recess 35 formed in the hammer dog element 40.

The rotating hammer element 50 is provided with a forward cylindrical skirt portion 50a slotted as at 51 and 52. The slots 51 and 52 are proportioned to receive the oppositely extending hammer dogs 14 and 15 so that the hammer dog element is guided axially in the slots 51 and 52 when the hammer dogs are moved in and out of the path of the anvil portions :12 and 13. The rotating hammer 50 is provided with a rearward skirt portion 50b which is adapted to telescope over the cylindrical exterior of the hammer dog 40. The rear end of the rotary hammer 50 includes a flange 50c terminating in the opening 50d.

The hammer dog element 40 is provided with a cam recess 41 adapted tocarry the ball 42 which is arranged to cooperate with the cam 23 carried by the cam shaft 18. FIG. 5 illustrates diagrammatically the cooperative relationship between the cam 23, the ball 42 and the cam recess 41.

Referring to FIG. 5 and assuming that the hammer dog element is being rotated in a counter-clockwise direction as indicated by the arrow 43, the cam 23 will tend to be held or restrained in space against rotation by the resistance to turning the not or bolt by means of the output shaft *8. Accordingly the ball 42 will be carried by the recess 41 and will roll along the cam surface 24 and thus carry the hammer dog element 40 axially in the direction of the arrow indicated at 44. The ball 42 will also roll along the periphery of the recess 41 until it reaches the right-hand end of this recess 41. The ball 42 is carried by the recess 41 to the highest point on the cam surface 24. This is the maximum advanced or forward position of the hammer dog unit 40 and is the impact position of the hammer dogs 14 and 15.

A similar operation occurs when the hammer dog element is rotated in a clockwise direction as indicated by the arrow 45. As shown in FIG. 5 the ball 42, in response to clockwise rotation of the hammer dog element 40, rolls along the base 23a of cam 23. Continued clockwise motion carries the ball up cam face 25 and is shown at the moment of impact between the hammer dogs 14 and 15 and the anvil. As will be understood as the description proceeds, the hammer dogs are retracted after impact and the ball 42, during retraction, will roll along the periphery of the recess 41 until the ball 42 is at the forward position in the recess 41 and on the base 23a of the cam 23. This latter position is the retracted position of the hammer dog element 40.

The relationship between the hammer dog and the cam means for advancing and retracting the hammer dog may be observed from FIGS. 6 and 7. When the hammer dog 40 is in its retracted position and the rotation of the driving element 39 is in the direction of the arrow 43, the ball 34 carried in the recess 33 of the driver element is disposed in the groove or pocket indicated at 36. One side of the ball 34 bears against the side of the pocket 36 and the other side of the ball 34 bears against the sloping wall 39 of the cam slot 35 in the hammer dog 40. In this way rotation as indicated at 43 is transmitted from the driver 30 to the hammer dog element 40. As the hammer dog is tinned in the direction of arrow 43, the recess 41 in the forward part of the hammer dog carries the ball 42 along the base 23a of the cam 23. In FIG. .6 the ball 42 is illustrated as riding along the base 23a of the cam and approaching the sloping wall 24 leading to the high point on the cam 23. In FIG. 7 the position of the parts indicates that the ball 42 has been carried up the cam face 24 and thus carried the hammer dog 14 forward into the path of the anvil 12.

During the advance of the hammer dog element 40 toward the anvil, the recess 35 formed in the hammer dog moves forwardly therewith and carries the ball 34 down the slope of the pocket 36 in the recess 33. After the energy of rotation of the hammer dog element 40 and the hammer 50 has been dissipated by the blow illustrated in FIG. 7, the sloping pocket 36 in the recess 33 cams the ball 34 along the sloping wall 39 of the recess 35 so as to restore the parts to the position illustrated in FIG. 6. In the event there is very little resistance to the turning of a bolt or nut, such as occurs when running up a nut on a bolt, the hammer dog 49 will move from the position of FIG. 6 to the position of FIG. 7 and will remain in the advanced position of FIG. 7 with the dog 14 bearing against the anvil portion 12 and thereafter the anvil h, hammer dog element 40 and hammer 50 will rotate in unison at the speed of the input motor. Resistance to turning thereafter will cause the hammer dog to be retracted as above described and thereafter an impact blow will be struck during each revolution.

To assemble the impact wrench shown in FIGS. 2 and 3, the cam shaft 18 is moved axially through the large open end of the hammer dog element 40 so as to trap the ball 42 between the recess 41 in the hammer dog element 40 and the cam 23 carried by the cam shaft. The rotating hammer 50 may be moved forwardly so as to place the hammer dogs 14 and 15 in the slots 51 and 52. Prior to assembly of the rotary hammer 50 over the hammer dog 49, the ball 34 is dropped into the triangular slot 35 in the hammer dog element and the ball 34 then rides in the cam recess 33 formed in the driver 30. A thrust bearing 46 is interposed between the end face of the cam 23 and the end face of the driver 30. The cam recess 33 in the driver 30 has one pocket 36 which slopes at about 60 with respect to the axis of the wrench and a second sloping pocket 37 also sloping at about 60 with respect to the axis of the wrench. The slot or cam openspouse ing 35 in the hammer dog member 40 has a sloping edge indicated at 38 and an oppositely sloping edge indicated at 39.

The apex of the triangular recess 33 in the driver 30 is disposed oppositely of the apex of the triangular opening 35 in the hammer dog element 40 so that in response to rotation of the driver 30 in a clockwise direction, the ball 34 is influenced so as to move along the pocket 37 and against the surface 38 of the opening 35 thus exerting a component axially of the wrench to retract the hammer dog element with respect to the anvil. Conversely when the driver 30 is rotated in a counter-clockwise direction, the ball 34 will roll along the pocket 36 and bear against the surface 39 so as to exert a component retracting the hammer dog element 40 from the anvil 9. The cooperating recesses and the sloping sides thereof in contact with the balls induces a rolling of the balls promoting long life in use.

During the operation of the impact wrench the splines on the driver 30 rotate in response to rotation of the motor shaft 32. The ball 34 transmits rotation of the driver to the hammer dog element 40 and the rotary member 50. The rotation of the hammer dog 40 carrying the ball 42 brings the ball into engagement with the cam face 25 on clockwise rotation and the cam face 24 on counter-clockwise rotation. The movement of the ball 42 in its rotational path imparts the axial movement of the hammer dog element 40 so that while it is being rotated, it is advanced towards the anvil and the faces on the hammer dogs 14 and 15 strike the anvil. As the faces of the hammer dog strike the anvil the energy of rotation stored in the rotating hammer and rotating hammer dog element 40 is imparted to the anvil and thence to the turning of the nut driven by the output shaft 8. When the energy of rotation is thus dissipated the cam surfaces in the recess 33 of the driver 30 and 35 of the hammer dog element 40 are effective to overcome the forces acting to hold the hammer dog 40 advanced. Accordingly the ball 34 and its cooperative cam recesses retract the hammer dogs 14 and 15 from the path of the anvil portions 12 and 13. The continued rotation of the motor is then effective to rotate the hammer 50 and the hammer dog element 40 one revolution and the operation is repeated so as to effect an impacting blow on the anvil as long as the anvil resists rotation.

Preferably the cam surfaces 24 and 25 which operate to advance the hammer dogs have a slope in the range between 30 and 40 with respect to the axis of the wrench. The sloping sides of the cam recess 33 and the driver are preferably in the range of between 60 and 70 with respect to the axis of the wrench to effect a quick retraction of the hammer dog immediately after an impacting blow. The impact wrench is well suited for running up" a nut prior to impacting. The inertia of the anvil and the cam shaft 18 provides a reaction for the ball 42 so that in running up a nut the hammer dog element 40 moves to its advanced position and exerts rotary torque against the anvil portions 12 and 13 with the result that the hammer 50, the hammer dog element 40 and anvil 9 rotate in unison. Under this condition of drive the hammer dog element 40 remains in advanced position.

In that form of the invention illustrated in FIGS. to 17, the input or motor shaft 32 is splined to rotate a driver 100. The driver 100 is provided with a cam recess 105 shaped substantially as in the preferred embodiment. A rotating hammer 106 is generally cylindrical in form and provides an interior bore to receive cam element 107 carried by the anvil 108. In this form of the invention the anvil 108 is provided with a portion 109 having opposite faces 110 and 111 adapted to be struck by an axially reciprocating hammer dog 112. The hammer dog 112 is shown in its retracted position in FIGS. 10 and 11, and in its advanced position in FIG. 12. The hammer dog shown in its entirety in FIG. 13 is mounted for axial reciprocation within an axial guideway 112a in the rotat- 0 ing hammer 106. The hammer dog 112 is provided with axially spaced spherical ball recesses 114 to cooperate with ball 115 and 116 to cooperate with ball 117.

The cam element 107 includes a cam 120 having oppositely sloping cam faces 121 and 122. The cam element 107 is journalled on the cam shaft 125 and the shaft 125 is fixed within the anvil 108. The anvil 108 is provided with a pair of radial faces 108a which are spaced 180 from each other. The cam element 107 is provided with an axially extending portion having opposite faces as at 1074:. The angular measurement between the faces 107a on the element 107 is less than the 180 between the faces 108a on the anvil. Preferably the angular dimension between the'faces 107a is such as to give the cam element 107 about 20 of lost motion before the face 107a is brought into engagement with a face 108a on the anvil.

engagement with the slope 120 and as the ball rolls along the slope 121 it advances the hammer dog 112 into the path of the anvil portion 109. The advanced position of the hammer dog as efiected by the cam 121 is illustrated in FIG. 12. The retracted position is illustrated in FIG. 11 which corresponds to the ball 117 being at the base 120a of the cam surface 120. Similarly when the motor shaft 32 imparts clockwise rotation as indicated by arrow 131, the ball 117 is brought into contact with the cam surface 122 so as to advance the hammer dog into the path of the anvil.

In the form of the invention shown in FIGS. 10 to 17, the driver 100 is provided with a recess substantially as in the first embodiment wherein two pockets 105a and 10511 are provided for the ball 115. The direction of rotation imparted to the driver 100 determines which pocket carries the ball 115. As in the preferred embodiment, the cam faces 121 and 122 are preferably in the range of about 30 to 40 and the slope of the cam pockets 105a and 105b is preferably in the range of 60 to 70". This form of my invention is also suited for running up a nut prior to impacting. -As soon as rotation is imparted to the driver 100, such drive is transmitted to the ball 115 and thence to the rotary hammer 106 and thence to the ball 117 so as to advance the hammer dog 112 into the path of the anvil. The hammer dog 112 bears against a face of the anvil such as 110 to rotate the anvil 108 until resistance is encountered. Thereafter the pockets 105a and 105b in the cam recess 105 are effective to retract the hammer dog 112. Thereafter each revolution of the hammer 1.06 and the dog 112 carried thereby results in an impacting blow.

It will be observed that in both forms of my invention the driver element which is splined to the motor shaft is provided with a ball recess which cooperates with a hall recess in the hammer dog so that a ball in the recesses transmits the rotation of the driver to the rotary hammer through the axially moving hammer dog carried in the rotating hammer. It will also be observed that in both forms of the invention a cam carried by the anvil cooperates with a ball carried by the hammer dog so as to advance the hammer dog into the anvil path for an impact blow.

In both forms of the invention as shown in the drawings described above, the ball recesses are constructed to elfect a rolling of the balls from one position to another as the hammer is advanced and retracted. The rolling referred to is desirable in that it prevents highloads being repeatedly imposed on certain areas of the cam recess or the ball. The halls and the cooperating recesses in which they roll function as a cam and cam follower. It will be understood by those skilled in the art that other arrangements of cam and cam follower may be employed.

In the form of impact wrench illustrated in FIGS. 10 to 17, the cam 120 and its cam shaft is caused to turn about in a direction opposite to the direction of rotation of the driver 100. The amount of such reverse rotation of the cam 120 is limited by the angular spacing between the face 167a on the cam and the face 108a on the anvil. As the ball 117 is pulled rearwardly by the retraction of the hammer dog 1'12, it rides rearwardly along the cam face 121 and theforce imparted thereto effects the reverse rotation of the cam shaft. In the form of impact wrench illustrated in FIGS. 1 to 9 it will be observed that the cam 23 on the shaft 18 may not turn reversely with respect to the direction of rotation of the driver. The cam shaft 18 is keyed to the anvil by means of the balls 20 and 21 and is thus restrained from any limited rotation with respect to the anvil as in the other embodiment. The lost motion required in order to permit the ball 42 to ride down the cam face 24 is accommodated by the peripheral branches of the recess 41.

Although I have described two forms of my invention in considerable detail, it will be appreciated by those skilled in the art that numerous modifications may be made therein without departing from the scope of the invention as defined in the following claims.

What is claimed is:

1. An impact wrench having a driver element mounted for rotation, an output shaft in alignment therewith mounted for rotation, said output shaft having oppositely disposed radially extending anvil portions carried thereby, a cam shw mounted in said output shaft and fixed thereto to rotate therewith, a cam on said cam shaft spaced axially from said anvil, a hammer dog having a first cylindrical portion surrounding said cam, said hammer dog having radially extending lugs, a slot formed at the interior of said cylindrical hammer dog portion, a ball mounted on said slot and proportioned to extend into the path of said cam, a cylindrical rotary hammer surrounding said hammer dog, said rotary hammer having axial slots therein to receive the lugs on said hammer dog, said hammer dog having a second cylindrical portion surrounding said driver element, said driver element having a cam recess within said second cylindrical portion, said hammer dog having a triangular opening in said second cylindrical portion aligned with the cam recess in the driver element, a ball mounted in said cam recess in the driver element proportioned to project into the opening in said second cylindrical portion whereby rotation of said driver element rotates said hammer dog and rotational movement of the hammer dog relative to the cam moves the hammer dog axially into the path of said anvil for an impacting blow.

2. An impact wrench having a driver element mounted for rotation, an output shaft in alignment therewith mounted for rotation, said output shaft having radially extending anvil portions carried thereby, a cam shaft mounted in Said output shaft to rotate therewith, a cam on said cam shaft, a hammer dog having a first cylindrical portion surrounding said cam, said hammer dog having radially extending lugs, a ball slot formed at the interior of said cylindrical portion, a ball mounted in said slot and proportioned to extend into the path of said cam, said hammer dog having a second cylindrical portion surrounding said driver element, said driver element having a cam recess within said second cylindrical portion, said hammer dog having an opening in said'seeond cylindrical portion aligned with the cam recess in the driver eelment, a ball mounted in said cam recess in the driver element proportioned to project into the opening in said second cylindrical portion whereby rotation of said driver element rotates said hammer dog and rotational movement of the hammer dog relative to the cam moves the hammer dog axially into the path of said anvil portions for an impacting blow.

3. An impact wrench comprising a motor housing having a motor shaft projecting therefrom, an impacting recess therein opposite the cam on said camshaft, a ball mechanism housing mounted on one end on said motor housing, an anvil shaft mounted in said impacting mechanism housing and projecting therefrom at the other endthereof, a driver element within said housing secured to said motor shaft to rotate therewith, said driver element having a shaft bore, a cam shaft having one end thereof mounted in said anvil shaft and fixed thereto to rotate therewith, the other end of said cam shaft being mounted in the shaft bore of said driver element, said driver element having a cam recess, a hammer dog having a cylindrical portion surrounding said cam shaft and said driver element, a cam on said cam shaft within said cylindrical portion, said cylindrical portion having a ball carried in said recess and projecting inwardly therefrom to engage said cam, said hammer dog cylindrical portion having a second ball recess formed therein, a ball carried by said recess and proportioned to project inwardly therefrom to ride in said cam recess on said driver element, a rotary hammer having a cylindrical portion surrounding the cylindrical portion of said hammer dog and covering said second hammer dog recess, radially extending overhanging portions on said hammer dog and said rotary hammer to guide the hammer dog for axial movement toward and away from said anvil whereby rotation of said driver element advances the hammer dog into the path of the anvil for an impacting blow, said driver element cam recess having an inclined side wall disposed at an angle to the axis of said shafts whereby said hammer dog is retracted from the path of the anvil after an impacting blow.

4. An impact wrench comprising a housing, an input shaft in one end of said housing, an output shaft at the other end of said housing, said output shaft having an anvil Within said housing, a driver element carried by said input shaft Within said housing, a cam shaft having one end thereof mounted within said output shaft, a cam on said cam shaft between the anvil and said driver element, a hammer dog mounted for rotary oscillatory rotary movement with respect to said cam shaft, said hammer dog having a forward section surrounding said cam and a rearward section surrounding said driver element, earn follower means on said forward section, said rearward section having a rear cam follower therein, said driver element having a cam recess therein to receive the said rear cam follower whereby rotation of the driver element rotates said rear cam follower to rotate the hammer dog and whereby rotation of the ham-mer dog moves said first-named cam follower relative to said cam and advances the hammer dog into the path of the anvil for an impacting blow and whereby torque applied subsequently to said impacting blow retracts the hammer dog from the path of the anvil.

5. An impact Wrench comprising a housing, an input shaft in one end of said housing, an output shaft at the other end of said housing, said output shaft having an anvil within said housing, a driver element carried by said input shaft within said housing, a cam shaft co-axial of the output shaft mounted between said output shaft and said driver element, a cam on said cam shaft, a hammer dog mounted for limited rotational movement with respect to said cam shaft and said driver element, said hammer dog having a first section surrounding said cam and a second section surrounding said driver element, a recess in said first section, said recess having two adjoining ball track portions wherein one ball track portion is offset axially with respect to the other ball track portion, a ball in said recess, said second section having a triangular recess formed therein, said driver element having a triangular ball recess therein, the apex of said driver element recess being disposed towards the anvil and the apex of the triangular recess in said second section being disposed towards said driver, a ballin said triangular recesses whereby rotation of the driver element rotates the ball disposed partly in the driver recess and partly in said hammer dog recess to rotate the hammer dog and whereby rotation of the hammer dog moves said first-named ball relative to said cam and advances the hammer dog axially into the path of the anvil for an impacting blow and whereby torque applied subsequently to said impacting blow retracts the hammer dog from the path of the anvil.

6. An impact wrench having a driver element, an anvil shaft co-axial with said driver element and axially spaced therefrom, said anvil shaft having an anvil lug eccentric of its axis and projecting axially from the anvil shaft toward said driver element, a cam shaft mounted [to turn with said anvil shaft and being rotatable relative to said driver element, a cam on said carn shaft, an axially movable hammer dog around said cam shaft between said driver element and said anvil shaft, a first cam follower on said hammer dog adjacent said cam and proportioned to bear against said cam, a second cam follower on said hammer dog, a cam recess in said driver element having the sides thereof disposed at an angle with respect to the axis of said driver element, said second cam follower proportioned to extend into the cam recess of said driver whereby rotation of said driver element rotates said second cam follower to rotate the hammer dog and whereby said first cam follower is carried rotationally relative to said cam to move the hammer dog axially into the path of said anvil to deliver an impacting blow.

7. An impact wrench having a driving element, an anvil shaft coaxial with said driving element and spaced therefrom, said anvil shaft having an anvil lug projecting axially therefrom toward said driving element, a cam shaft secured at one end thereof in said anvil shaft and rotatably mounted at the other end thereof in said driving element, a cam on said cam shaft, a rotary hammer surrounding said cam and said driving element, an axially movable hammer dog carried by said rotary hammer, a first cam recess on said hammer dog adjacent said cam and a first ball mounted in said recess and arranged to project inwardly thereof to bear against said cam, a second cam recess on said hammer dog, a second ball in the second cam recess, a cam recess in said driver element to receive a portion of said second ball whereby rotation of said driving element rotates said second ball to rotate the hammer dog and thereby rotate the rotary hammer and whereby said first-named ball is carried rotationally relative to said cam to move the hammer dog axially into the path of said anvil to deliver an impacting blow.

8. An impact wrench comprising a motor shaft, a driver element splined to said motor shaft, said driver element having an axial bore therein, a cam shaft having one end thereof mounted in said bore, an anvil shaft having a bore therein, said cam shaft having its other end mounted in the bore of the anvil shaft, an anvil carried by said anvil shaft having an anvil face portion eccentrically of the axis of the anvil shaft, a cam recess in said driver element, a cam on said cam shaft intermediate said driver element and said anvil, interlocking means between said cam shaft and said anvil shaft to provide for joint rotation of the cam shaft and the anvil shaft, an axially slidable hammer dog having axially spaced recesses therein, said first recess having a first means therein and projecting inwardly therefrom to bear against said cam, said second hammer dog recess having second means therein and projecting inwardly therefrom into the cam recess of said driver element, a rotary hammer surrounding said driver element and said cam, said rotary hammerhaving axial guide means for said hammer dog whereby rotation of said driver element transmits rotation to said hammer dog through said second means and whereby rotation of the hammer dog and the first means carried thereby, moves the hammer dog axially into the path of said anvil portion to deliver an impacting blow thereto and whereby the hammer dog is withdrawn from the path of the anvi'i portion subsequent to the impacting blow.

9. An impact wrench comprising a motor shaft, a driver element fixed to said motor shaft, an anvil shaft mounted for rotation co-axially of said driver element and spaced axially therefrom, a cam shaft co-axial with the anvil shaft mounted between the driver element and the anvil shaft, an anvil carried by said anvil shaft having an anvil face portion eccentrically of the axis of the anvil shaft, a cam recess in said driver element, a cam on said cam shaft intermediate said driver element and said anvil, interlocking means between said cam shaft and said anvil shaft to provide for joint rotation of the cam shaft and the anvil shaft, an axially slidable hammer dog, said hammer dog having a first cam follower means carried thereby and projecting inwardly therefrom to bear against said cam, said hammer dog having second cam follower means carried thereby and projecting inwardly therefrom into the cam recess of said driver element, a rotary hammer surrounding said driver element and said cam element, said rotary member having axial guide means to guide said hammer dog axially thereof whereby rotation of said driver element transmits rotation to said hammer dog through said second cam follower means and whereby rotation of the hammer dog and the first cam follower means carried thereby moves the hammer dog axially into the path of said anvil portion to deliver an impacting blow.

10. An impact wrench comprising a housing, a rotating driver element at one end of said housing, an anvil shaft mounted for rotation in the other end of said housing, a cam shaft carried by said anvil shaft, a cam on said cam shaft, said cam having a sloping cam face formed thereon, said driver element having a sloping cam recess formed therein, a hammer dog mounted for axial movement toward and away from said anvil shaft, said anvil shaft having an anvil portion eccentrically thereof and extending radially into alignment with said hammer dog, said hammer dog having spaced ball recesses thereon, a first ball recess having a ball therein and projecting therefrom to engage said sloping cam surface, said second ball recess having a ball therein and projecting therefrom into the cam recess in said driver element, said cam recess in the driver element having sides sloping with respect to the axis of the driver element at a steeper angle than the slope of the face on said cam whereby rotation of said driver element imparts rotation to said hammer dog and rotation of the hammer dog carries said firstnamed hall rotationally with respect to said cam and whereby said second-named ball rolls along said sloping cam surface and projects the hammer dog axially into the path of the anvil portion to deliver an impacting blow, a rotary hammer surrounding said hammer dog, said rotary hammer having means to guide the hammer dog axially into and out of the path of the anvil, said driver element recess having the said sloping sides thereof inclined with respect to the axis of the driver element in the range of 60 to 70 and the sloping face of said cam being disposed at an angle in the range of 30 to 40 with respect to the same axis whereby the hammer dog is retracted from the path of the anvil after an impacting blow is imparted to the anvil by the hammer dog.

11. An impact Wrench comprising a housing, a rotating driving element at one end of said housing, an avil shaft mounted for rotation in the other end of said housing, a cam shaft fixed to said anvil shaft and projecting axially therefrom towards said driver element, a cam on said cam shaft having a face formed thereon, said face sloping at about 35 with respect to the axis of the cam shaft, said driver element having a cam recess formed thereon, said recess having sides sloping at about 60 with respect to the axis of the cam shaft, a hammer dog mounted for axial movement toward and away from said anvil shaft, said anvil shaft having an anvil portion eccentrical- 1y thereof and extending radially into alignment with said hammer dog, said hammer dog having spaced ball recesses thereon, a first ball recess having a ball therein and projecting therefrom to engage said sloping cam face, said second ball recess having a ball therein and projectingtherefrom into the cam recess in said driver element whereby rotation of said driver element imparts rotation to said hammer dog and rotation of the hammer dog carries said first-named ball rotationally with respect to said cam face and whereby said second-named ball rolls along said cam face and projects the hammer dog into the path of the anvil to deliver an impacting blow.

12. An impact wrench comprising a housing, a driving member mounted for rotation at one end of said housing, a driven member mounted for rotation at the other end of said housing, said driven member having an anvil carried eccentrically thereof within the housing, said driving member having an axial bore therein, said driven member having an axial bore therein, a cam shaft extending into the bore of the driven member at one end thereof and into the bore of the driving member at the other end thereof, said cam shaft being secured against relative rotation with respect to said driven memher, a cam carried by said cam shaft, said cam having a radially disposed cam face eccentric of the axis of the cam shaft and sloping at an angle of about 35 with respect to the axis of the cam shaft, said driving member having a recess at its exterior, said recess having sides sloping with respect to the axis of the cam shaft at an angle of about 60, a hammer dog having a forward hall recess adjacent said cam and a rearward ball recess adjacent the recess in the driving member, a ball mounted in said forward recess and proportioned to project therefrom into engagement with said cam face, a ball in said rearward recess projecting into the recess of the driving member, a rotating hammer surrounding said driving member, said rotary hammer having guide means to guide said hammer dog for axial movement whereby rotation of the hammer dog moves the ball in said forward recess into engagement with the sloping face of said cam and projects the hammer dog axially into the path of the anvil for an impact blow whereby said hammer dog is retracted from the path of the anvil immediately follow ing an impact blow.

13. An impact wrench comprising a housing, a driving member mounted for rotation at one end of said housing, a driven member mounted for rotation at the other end of said housing, said driven member having an anvil carried eccentrically thereof within the housing, a cam shaft mounted between the driving and driven members, said cam shaft being mounted against relative rotation with respect to said driven member, a cam carried by said cam shaft, said cam having a cam face sloping with respect to the axis of the cam shaft, said driving member having a cam recess at its exterior, said cam recess having sides sloping with respect to the axis of the cam shaft, a hammer dog having a forward ball recess adjacent said cam and a rearward ball recess adjacent the cam recess in the driving member, a ball mounted in said forward recess and proportioned to project therefrom into engagement with said sloping cam face, a ball in said rearward recess projecting into the cam recess of the driving member, a rotary hammer driven by said hammer dog, said rotary hammer having guide means to guide the hammer dog for axial movement whereby rotation of the hammer dog moves the ball in said forward recess into engagement with the sloping face of said cam and projects the hammer dog axially into the path of the anvil.

14. An impact wrench comprising a motor having a shaft, an impact wrench housing mounted on said motor, an anvil shaft journaled in said housing having an output portion extending from said wrench housing, an anvil carried by said anvil shaft within said housing, a cam shaft. carried by said anvil shaft, a driver element fixed to said motor shaft so asto be driven thereby, a cylindric'al. hammer. dog. member surrounding saidcam shaft,

a cam on said cam shaft within said cylindrical hammer dog, a recess in the hammer dog adjacent said cam, a rotary hammer mounted on said hammer dog, said rotary hammer having guide means therein to receive portions of said hammer dog and guide the hammer dog for axial movement relative to the rotary hammer, and a ball carried in the recess of the hammer dog adjacent said cam to bear against said cam whereby rotation of the hammer dog relative to said cam moves the hammer dog axially into the path of said anvil to deliver an impact blow.

15. An impact wrench comprising a motor having a driving shaft, an impact wrench mounted on the motor in alignment with said driving shaft, said wrench including an anvil shaft having an output portion extending therefrom, an anvil carried by said anvil shaft, a cam shaft carried by said anvil shaft in alignment with said driving shaft, 21 driver element fixed to said driving shaft so as to be driven thereby, said driver element having a cam element thereon, a cylindrical hammer dog member surrounding said cam shaft and said driver element, a cam on said cam shaft within said cylindrical hammer dog, a recess in the hammer dog at the forward end thereof adjacent said cam, a cam element on said hammer dog at the rear end thereof adjacent said driver, a cylindrical rotary hammer surrounding said hammer dog, said rotary hammer having slots therein to receive projecting portions of said hammer dog and guide the hammer dog for axial movement relative to said rotary hammer, and a ball carried in the forward recess of the hammer dog adjacent the cam to bear against said cam whereby rotation of the hammer dog relative to said cam moves the hammer dog axially into the path of said anvil to deliver an impact olow.

16. In an impact wrench, a motor driven driver element, a driven element having an anvil carried thereby in a rotary path, a rotatable hammer, a hammer dog mounted within said hammer between said driver element and said driven element for axial movement in and out of said anvil path, a first cam-and cam follower means connecting said hammer dog to said driver element for rotating the hammer dog and hammer and retracting the hammer dog from the anvil path, and a second cam and cam follower means connecting said hammer dog to said anvil to advance the hammer dog into the path of the anvil for delivery of an impact blow.

17. In an impact Wrench, 21 motor driven driver element, a driven element having an anvil carried thereby in a rotary path, a cam shaft carried by said driven element, a hammer dog mounted between said driver element and said driven element for axial movement in and out of said anvil path, a first cam and cam follower means connecting said hammer dog to said cam shaft to ad- Vance the hammer dog into the anvil path for delivery of an impact blow, and a second cam and cam follower means between said first cam and cam follower means and said driver element connecting said hammer dog to said driver element for rotating the hammer dog and retracting the hammer dog from the anvil path.

18. An impacting wrench having a housing, a motor shaft extending into said housing at one end thereof, a driver element fixed on said one end, an anvil shaft journaled at the other end of said housing, said anvil shaft having a radial face within the housing, spaced anvil lugs projecting axially from said radial face, a cam shaft mounted in alignment with said anvil shaft and said driver element, said cam shaft being free to rotate with respect to said driver element and being coupled to the anvil shaft to rotate therewith, a cam on said cam shaft, a hammer dog having a first section surrounding said cam and a second section surrounding said driver element, said second section having cam means thereon, said driver element having cam means co-operable with said cam means on said second section to rotate said hammer dog and retract the hammer dog from the path ofsaid anvil lugs, said first section having a cam follower carried thereby and proportioned to project inwardly therefrom and bear against said cam, said cam having an inclined cam face whereby rotation of the hammer dog in one direction brings said cam follower into engagement with said cam face and moves the hammer dog axially with respect to the cam shaft and into engagement with the anvil lugs.

19. In an impact wrench, a motor-driven driver element, a driven element having wrench socket portions at one end thereof and an anvil at the other end thereof, said anvil having projecting anvil lugs, a cam shaft carried by said driven element and projecting axially therefrom toward said driver element, a hammer dog surrounding said cam shaft and mounted between said driver element and said driven element for axial movement therealong in and out of the path of said anvil lugs, first cam means formed on said driver element and cam follower means on said hammer dog for rotating the hammer dog and retracting the hammer dog from the path of the anvil lugs, and second cam means on said cam shaft and cam follower means on the hammer dog connecting the hammer dog to the cam shaft to advance the hammer dog into the path of the anvil lugs for delivery of an impacting blow.

References Cited in the file of this patent UNITED STATES PATENTS 2,219,865 Fitch Oct. 29, 1940 2,533,703 Wilhide et al. Dec. 12, 1950 2,712,254 Schodeberg July 5, 1955 2,745,528 Amtsberg May 15, 1956 FOREIGN PATENTS 7 1,057,422 France Oct. 28, 1953 1,091,048 France Oct. 27, 1954 

